Nanostructure and biomolecule interactions : Characterizing the complex

Sammanfattning: This thesis presents the results of studies done on various biomolecules and their interactions with nanomaterials. The biomolecule sources are everything from purified, single proteins to the complicated mixture of blood serum and cell culture media. Similarly, the nanomaterial sources vary from spherical titanium dioxide, gold, and polystyrene nanoparticles to novel nanowires of gallium arsenide or gallium phosphide. Regardless of the biomolecules or nanomaterials, they interact in ways that require careful characterization in case the environment and organisms are exposed to theses increasingly common materials. The adsorbed protein layer on a nanostructure is called the protein corona and the nanomaterial together with its adsorbed biomolecules is called a complex.We show that when titanium dioxide nanoparticles are mixed with blood serum, a broad range of complex sizes are formed.Traditionally, the protein corona has been considered homogeneous for specific nanoparticle and serum concentration ratio.However, our results show that the corona varies with the complexes’ size.We also look at the effect protein has on very low concentration of 20 nm gold nanoparticles in cell culture medium. Using acombination of analytical techniques, we show that in protein enriched cell culture medium, the nanoparticles are stable. In cellculture medium without added protein, the nanoparticles aggregate slowly. We describe the aggregation rate and the aggregatemorphology and identify arginine, an aggregation inducing amino acid in the biomolecular corona.Furthermore, we study the binding of purified proteins on nanowires by cryo-transmission electron microscopy, X-ray basedanalytical techniques, and by changes in the sedimentation rate of nanowires with and without adsorbed protein layer. By rotatingthe electron microscope stage during imaging, we can image irregularities in the protein corona formed by the large, cross shaped protein laminin.Finally, we study the effect of various nanostructures on the activity of the enzyme myeloperoxidase. The nanostructures’ effectwas highly dependent on the complexity of the environment. The effect ranged from almost total inactivation to increasing theactivity up to three-fold.